Women who are both obese and taking oral contraceptives are at an increased risk for cerebral venous thrombosis (CVT), according to a study published in JAMA Neurology.1

Obesity has been previously identified as a risk factor for venous thromboembolism (VTE), however the potential relationship between obesity and the rare CVT is not well known.

Susanna Zuurbier, MD, of the Department of Neurology at the Academic Medical Centre in Amsterdam, and colleagues performed a case-control study in adult patients with CVT and compared them to controls from the Multiple Environmental and Genetic Assessment of Risk Factors for Venous Thrombosis study.

In total, 186 patients with CVT and 6134 controls were included in the study after excluding pregnant or recently pregnant participants. Compared to the controls, the participants with CVT were female (71.5% vs 52.5%), used oral contraceptives (72.9% vs 23.5% of women), were younger (40 vs 48 years of age), and had a history of cancer (9.1% vs 3.8%). Participants with CVT also had a higher mean BMI (26.7 vs 25.6, P=.01). After adjustment, the investigators found a greater risk of CVT in participants with obesity (BMI ≥30, aOR 2.63, 95% CI: 1.53-4.54) but not overweight participants. There was a similar association observed for CVT in women who were overweight or obese (BMI 25-29.9, aOR 1.71, 95% CI: 1.01-2.91; BMI≥30, aOR 3.50, 95% CI: 2.00-6.14) but not in men.

The authors pointed out that although the absolute risk of CVT is small, obese women should be counseled on the potential risks of using oral contraceptives.

“To our knowledge, this is the first case-control study that examined the association between obesity and CVT. Our results suggest that obesity is associated with a substantially increased risk of CVT in women who use oral contraceptives. This increased risk should be taken into consideration when prescribing oral contraceptives to obese women,” the authors concluded.1

In an accompanying editorial, Chirantan Banerjee, MD, MPH, of the Department of Neurology at the Medical University of South Carolina in Charleston, highlighted that the novel findings “demonstrate a dose-response relationship in the risk of CVT among women using OCs, with obese women having a higher risk compared with overweight women.” Dr Banerjee did, however, note several limitations including missing BMI data in 15.9% of cases, the use of unmatched controls, and a small sample not taking oral contraceptives.2

“The authors correctly point out that despite the manifold increased relative risk, the absolute risk of CVT in obese women taking OCs still remains low and should not preclude OC use among them.”

The study was funded by grants from The Netherlands Organisation for Scientific Research, the Dutch Thrombosis Society, the Remmert Adriaan Laan Foundation, and the Swiss Heart Foundation. Dr Arnold reported honoraria from pharmaceutical companies.